A powerful new Japanese spacecraft and experimental solar sail have blasted off together to start a six-month trek to explore Venus and cosmic parts beyond.

One mission is aimed at uncovering the secrets of Venus and its cloud-covered surface, while the other could become the first interplanetary solar sail to fly successfully in space. The Japan Aerospace Exploration Agency, or JAXA, is backing both spaceflights.

A Japanese H-2A rocket lifted off with the Venus Climate Orbiter, named Akatsuki, as its main payload at 6:58 a.m. Friday local time (5:58 p.m. ET Thursday) from the Tanegashima Space Center.

The Akatsuki spacecraft's name means "Dawn" in Japanese. If all goes well, it should arrive at Venus in December.

JAXA had hoped to launch Akatsuki and its Ikaros solar sail companion on Tuesday, but low clouds and foul weather prevented liftoff at that time.

Unveiling Venus
Akatsuki has set sights on a planet that scientists regard as Earth's moodier, more hellish twin.

One of the main goals is to understand the "super-rotation" of the Venus atmosphere, where violent winds drive storms and clouds at speeds of more than 220 mph (360 kilometers per hour), 60 times faster than the planet itself rotates.

"Akatsuki is the first 'meteorological satellite' of a planet other than Earth," said Seiichi Sakamoto, director for space science outreach at JAXA's Institute of Space and Astronautical Science. "Detailed study of Earth's sister planet will provide us with breakthroughs in the field of atmospheric science."

Solar sail rides shotgun
Japan's new solar sail, named Ikaros (
Interplanetary
Kite-craft
Accelerated by
Radiation
Of the
Sun), also hitched a ride as one of five smaller secondary payloads built by private universities and corporations.

The solar sail craft will take the same starting trajectory as Akatsuki, but is scheduled to pass the orbit of Venus during an ambitious three-year journey to the other side of the sun.

Ikaros is designed to rely only upon the pressure of sunlight to push it along, but it also carries thin-film, electricity-generating solar cells embedded within its kitelike frame. Such a design might allow future spacecraft to draw electricity for ion-propulsion engines, even as they also use the solar sail for backup — not unlike a sailing boat that also uses a solar-powered engine.

The mission launch involved an unusual maneuver for the H-2A rocket, which typically separates its main payload before the smaller payloads.

"This time we separated three piggyback satellites before Akatsuki," Sakamoto told Space.com. "This is new to H-2A."

A JAXA publicity campaign to send names and messages to Venus has received more than 260,000 submissions from around the world, according to Sakamoto. Akatsuki's study of Venus is planned to last at least two years after it enters the planet's orbit.

The Japanese space agency launched a new space freighter late last year aboard an H-2B rocket, which represents the newer and bigger descendant of the H-2A rocket that kicked off the Venus mission.